regardless of background, children with lower general verbal ability and those who have difficulty with phonetic processing seem to struggle

This fall, Hoeft and her colleagues at U.C.S.F. published the results of a three-year longitudinal study looking at the basic neuroscience of reading development

In addition to undergoing a brain scan, the children were tested for general cognitive ability, as well as a host of other factors, including how well they could follow instructions and how coherently they could express themselves

Each parent was also surveyed, and each child’s home life, carefully analyzed: How did the child spend her time at home? Was she read to frequently? How much time did she spend watching television? Three years later, each child’s brain was scanned again, and the children were tested on a number of reading and phonological tests

When Hoeft took into account all of the explanatory factors that had been linked to reading difficulty in the past—genetic risk, environmental factors, pre-literate language ability, and over-all cognitive capacity—she found that only one thing consistently predicted how well a child would learn to read. That was the growth of white matter in one specific area of the brain, the left temporoparietal region.

The amount of white matter that a child arrived with in kindergarten didn’t make a difference. But the change in volume between kindergarten and third grade did

Information, in the form of electrical signals, runs across the white matter, allowing for communication between the different parts of the brain: you see something, you give it meaning, you interpret that meaning

Her results suggested that, if the increase in white matter doesn’t occur at the critical time, children will have a hard time figuring out how to look at letters and then turn them into words that have meaning

Hoeft’s discovery builds on previous research that she conducted on dyslexia. In 2011, she found that, while no behavioral measure could predict which dyslexic children would improve their reading skills, greater neural activation in the right prefrontal cortex along with the distribution of white matter in the brain could, with seventy-two-per-cent accuracy, offer such a prediction

Over-all intelligence and I.Q. didn’t matter; what was key was a very specific organizational pattern within your brain

Our findings could be interpreted as meaning that there’s still genetic influence,

it’s also likely that the dorsal white-matter development is representing the environment the kids are exposed to between kindergarten and third grade. The home environment, the school environment, the kind of reading instruction they’re getting

Hoeft and her colleagues try to turn their understanding of reading ability toward helping to identify the most effective teaching methods that could help develop it

She’s studied, in particular, a concept known as stealth dyslexia: people who have all of the makings of dyslexia or other reading problems, but end up overcoming them and becoming superior readers

Studying stealth dyslexics, Hoeft posits, could be key to figuring out how to improve reading education more broadly. These stealth dyslexics have reading problems but are able to develop high comprehension all the same

Hoeft’s group, she told me, has found that stealth dyslexics display a unique dorsolateral prefrontal cortex. That’s the part of the brain that is responsible, among other things, for executive function and self-control. In stealth dyslexics, it seems to be particularly well-developed. That may be partly genetic, but, Hoeft says, it may also point to a particular educational experience: “If it’s superior executive function that is helping some kids develop despite genetic predisposition to the contrary, that is really good news, because that is something we do well—we know how to train executive function.”

That might mean that, in the earliest stages, we need to pay attention to that executive function,” she says. “We need to start not just giving flashcards, letters, and sounds the way we now do, but, especially if we know someone might be a problem reader, look at these other skills, at cognitive control and self-regulation.”